BZOJ3306 树

话说出题人你们能不能有点新意。。。都叫tree / 树真的大丈？！

题解：Orz 千古神犇ZYF！

  1 /**************************************************************
  2     Problem: 3306
  3     User: rausen
  4     Language: C++
  5     Result: Accepted
  6     Time:1644 ms
  7     Memory:22996 kb
  8 ****************************************************************/
  9
 10 #include <cstdio>
 11 #include <algorithm>
 12
 13 using namespace std;
 14 const int N = 100005;
 15 const int M = 400005;
 16 const int inf = 1e9;
 17
 18 struct edge {
 19     int next, to;
 20     edge() {}
 21     edge(int _n, int _t) : next(_n), to(_t) {}
 22 } e[N];
 23
 24 int cnt_edge, first[N];
 25
 26 struct tree_node {
 27     int v, dep, st, ed, fa[17];
 28 } tr[N];
 29
 30 struct seg_node {
 31     seg_node *lson, *rson;
 32     int l, r, mn;
 33 } *seg_rt, mempool[M], *cnt_seg = mempool;
 34
 35 int n, root;
 36 int q[N], cnt_seq;
 37
 38 inline int read() {
 39     int x = 0, sgn = 1;
 40     char ch = getchar();
 41     while (ch < ‘0‘ || ‘9‘ < ch) {
 42         if (ch == ‘-‘) sgn = -1;
 43         ch = getchar();
 44     }
 45     while (‘0‘ <= ch && ch <= ‘9‘) {
 46         x = x * 10 + ch - ‘0‘;
 47         ch = getchar();
 48     }
 49     return sgn * x;
 50 }
 51
 52 inline void add_edge(int x, int y) {
 53     e[++cnt_edge] = edge(first[x], y);
 54     first[x] = cnt_edge;
 55 }
 56
 57 void dfs(int p) {
 58     int x;
 59     q[tr[p].st = ++cnt_seq] = p;
 60     for (x = 1; x <= 16; ++x)
 61         tr[p].fa[x] = tr[tr[p].fa[x - 1]].fa[x - 1];
 62     for (x = first[p]; x; x = e[x].next) {
 63         tr[e[x].to].dep = tr[p].dep + 1;
 64         dfs(e[x].to);
 65     }
 66     tr[p].ed = cnt_seq;
 67 }
 68
 69 #define Lson p -> lson
 70 #define Rson p -> rson
 71 #define Mn p -> mn
 72 #define L p -> l
 73 #define R p -> r
 74 #define mid (L + R >> 1)
 75 inline void seg_update(seg_node *p) {
 76     Mn = min(Lson -> mn, Rson -> mn);
 77 }
 78
 79 void seg_build(seg_node *&p, int l, int r) {
 80     p = ++cnt_seg, L = l, R = r;
 81     if (l == r) {
 82         Mn = tr[q[l]].v;
 83         return;
 84     }
 85     seg_build(Lson, l, mid), seg_build(Rson, mid + 1, r);
 86     seg_update(p);
 87 }
 88
 89 void seg_modify(seg_node *p, int pos, int v) {
 90     if (L == R) {
 91         Mn = v;
 92         return;
 93     }
 94     if (pos <= mid) seg_modify(Lson, pos, v);
 95     else seg_modify(Rson, pos, v);
 96     seg_update(p);
 97 }
 98
 99 int seg_query(seg_node *p, int l, int r) {
100     if (l > r) return inf;
101     if (L == l && r == R) return Mn;
102     if (r <= mid) return seg_query(Lson, l, r);
103     else if (mid < l) return seg_query(Rson, l, r);
104     else return min(seg_query(Lson, l, mid), seg_query(Rson, mid + 1, r));
105 }
106
107 int main() {
108     int i, Q, now, x, v;
109     char st[10];
110     n = read(), Q = read();
111     for (i = 1; i <= n; ++i) {
112         tr[i].fa[0] = read(), tr[i].v = read();
113         if (tr[i].fa[0]) add_edge(tr[i].fa[0], i);
114     }
115     tr[root = 1].dep = 1;
116     dfs(1);
117     seg_build(seg_rt, 1, n);
118     while (Q--) {
119         scanf("%s", st + 1), x = read();
120         if (st[1] == ‘V‘)
121             seg_modify(seg_rt, tr[x].st, read());
122         else if (st[1] == ‘E‘) root = x;
123         else {
124             if (root == x) printf("%d\n", seg_rt -> mn); else
125             if (tr[x].st <= tr[root].st && tr[root].ed <= tr[x].ed) {
126                 for (i = 16, now = root; ~i; --i)
127                     if (tr[tr[now].fa[i]].dep > tr[x].dep) now = tr[now].fa[i];
128                 printf("%d\n", min(seg_query(seg_rt, 1, tr[now].st - 1), seg_query(seg_rt, tr[now].ed + 1, n)));
129             } else
130             printf("%d\n", seg_query(seg_rt, tr[x].st, tr[x].ed));
131         }
132     }
133     return 0;
134 }